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I have a three camera dash cam (front, rear, cabin). The front is 2160p and the rear is 1080p. I would like to combine two simultaneous videos (front and rear) into one 3840 x 4320 video (stacked vertically, 1080p upscaled) without producing a gigantic file.

I tried to do this in OpenShot with a custom profile, and it was "successful" in that the video was formatted correctly... but it was 17GB and took 5 hours to render on my 5950x. The source files are 2:00 long and 240MB and 80MB respectively. I would like a video similar in size to the combined size of the source videos.

Any tips on how to combine them without a bloated, rendered vid?

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The reason your exported file is huge is likely to be due to the Export settings chosen when you exported. The resolution you're planning to export at (3840 x 4320) is larger than 4K which is realistically the largest format most people use for viewing videos.

I would try re-exporting your final video as an mp4 video with an h264 codec at 3840x2160 resolution with a bitrate of 12Mb/s, and see how the exported video looks in terms of quality and file size.

Quality and file size are a trade-off. For a given codec and resolution & frame rate, larger files (higher bit rate) will result in higher quality files.

I don't know the OpenShot software, but from the look of the manual, you can manually adjust the export settings in this window:

enter image description here

YouTube has a guide to bitrates etc here which is useful for working out export formats even if you don't want to publish to youtube:

https://support.google.com/youtube/answer/1722171?hl=en#zippy=%2Cbitrate

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  • So there's no easy way to just use their existing bitrates and file sizes to infer a reasonable bitrate for the combined video? That's the frustrating part for me. I don't understand why the file sizes aren't marginally additive (obviously somewhat bigger for the upscaling of the 1080p video)
    – cma0014
    Commented Jul 11 at 18:15

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